Iliopsoas Muscle

Author: Scott A. Sheffield MS

Last update:

The image descriptioniliopsoas is composed of two muscles: the iliacus and psoas major. Along with the psoas minor, these muscles form the group of inner hip muscles.

Located deep within the pelvic region, the iliopsoas muscle spans between the hip bone and femur, serving a variety of functions for the hip joint. This article will discuss the anatomy and functions of this muscle.

Iliacus muscle
OriginIliac fossa;
Iliac crest.
InsertionLesser trochanter of the femur (via shared tendon with psoas major)
InnervationFemoral nerve
FunctionsTogether with psoas major: Flexion and external rotation of the thigh;
Psoas major muscle
OriginTransverse processes of lumbar vertebrae L1-L5;
Bodies of T12-L5 and their intervertebral discs.
InsertionLesser trochanter of the femur (via shared tendon with iliacus)
InnervationAnterior rami of lumbar spinal nerves L1-L3
FunctionsTogether with iliacus: Flexion and external rotation of the thigh;
Contracting alone: Lateral flexion of the trunk
An illustration showing an anterior view of the hip girdle muscles and the Iliopsoas muscle is labeled and highlighted with green
Iliopsoas muscle
1

Origin and Insertion

The psoas major and iliacus muscles have distinct origins but share a joint insertion. The iliacus muscle image descriptionoriginates from the iliac fossa and iliac crest. The psoas major image descriptionoriginates from the transverse processes of lumbar vertebrae L1-L5 and some adjacent structures, including the bodies of T12-L5 vertebrae and the intervertebral discs between them.

Both muscles converge towards the femur, and via a shared tendon, they insert onto the lesser trochanter of the femur.

Anterior view of the thigh, pelvis and lower section of the vertebral column showing the origin of Iliacus at the iliac fossa of os coxa and the insertion at the lesser trochanter of femur.
The anterior view of the thigh, pelvis and lower section of the vertebral column showing the attachments of Psoas Major muscle with the origin at the bodies and bases of transverse processes of L1-L5 and insertion on the lesser trochanter of the femur.
Origin and insertion
1
2

Innervation

The two components of the iliopsoas muscle have different innervations:

  • Psoas major is innervated by the anterior rami of lumbar spinal nerves L1-L3
  • Iliacus is innervated by the femoral nerve

Solidify your knowledge of the anatomy of the back muscles with more in-depth articles.

Functions

The iliopsoas muscle is the primary and .  When the insertion is the fixed point, the psoas major contributes to the flexion of the trunk during bilateral contraction (contraction from both sides). When only one psoas major contracts in this manner (unilateral contraction), it aids in the lateral flexion of the trunk.

Slide 1 of the animation showing flexion of the thigh.
Slide 2 of the animation showing flexion of the thigh.
Slide 3 of the animation showing flexion of the thigh.
Slide 4 of the animation showing flexion of the thigh.
Slide 5 of the animation showing flexion of the thigh.
Flexion of the thigh at the hip joint

Test yourself

Muscles That Act On The Anterior Thigh (From The Hip)

A quiz image of the anterior view of the thigh, pelvis and lower section of the vertebral column. The muscles of the anterior thigh are numbered 1 to 9 and the answers are concealed.
A quiz image of the anterior view of the thigh, pelvis and lower section of the vertebral column. The muscles of the anterior thigh are numbered 1 to 9. The answers revealed at the bottom are as follows 1. Psoas Major 2. Iliacus 3. Tensor Fasciae Latae 4. Pectineus 5. Adductor Longus 6. Rectus Femoris 7. Vastus Lateralis 8. Sartorius 9. Gracilis.
1
2

References

  • Open Anatomy. (n.d.). TA2 Viewer. Retrieved April 5, 2023, from https://ta2viewer.openanatomy.org/
  • Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., & Kruse, D. H. (2022). Anatomy and Physiology (2nd ed.). OpenStax. https://openstax.org/details/books/anatomy-and-physiology-2e
  • Palastanga, N., & Soames, R. (2012). Anatomy of Human Movement (6th ed.). Edinburgh, Scotland: Churchill Livingstone.
  • Moore, K. L. (2018). Clinically Oriented Anatomy (8th ed.). Philadelphia, PA: Wolters Kluwer.
  • Drake, R. L., Vogl, A. W., & Mitchell, A. W. M. (2015). Gray’s Anatomy for Students (3rd ed.). Edinburgh, Scotland: Churchill Livingstone.
Related Articles
Anterior view of the hip and femur showing the vastus medialis muscle
Vastus Medialis Muscle

Vastus Medialis Muscle (Insertion, Origin, Actions & Innervations); explained beautifully in an illustrated and interactive way.
Vastus Lateralis Muscle - Featured
Vastus Lateralis Muscle

Vastus Lateralis Muscle (Insertion, Origin, Actions & Innervations); explained beautifully in an illustrated and interactive way.
Anterior view of the hip and femur showing the vastus intermedius muscle
Vastus Intermedius Muscle

Vastus Intermedius Muscle (Insertion, Origin, Actions & Innervations); explained beautifully in an illustrated and interactive way.